Field of the Invention
The invention relates to the field of fluid dynamics, and particularly to the fluid flow relative to a surface such as a lifting and/or thrust-generating body.
Related Art
Various methods of wake vortex control and drag alleviation have been proposed in the prior art. These include control surface oscillations, wingtip devices, multi-wake interactions, thermal forcing and mass/momentum injection. Various methods which promote mixing using corrugated, serrated or convoluted surfaces or control surfaces have been proposed for reducing drag. See, e.g., Sinous Chevron Exhaust Nozzle, U.S. Patent Publication US 2005/0172611; Method and Device for Reducing Engine Noise, U.S. Pat. No. 7,240,493 B2; System and Method of Vortex Wake Control using Vortex Leveraging, U.S. Pat. No. 6,042,059; Undulated nozzle for enhanced exit area mixing, U.S. Pat. No. 6,082,635; Airfoil trailing edge, U.S. Pat. No. 4,813,633; Two-stage mixer ejector suppressor, U.S. Pat. No. 5,761,900; Diffuser with convoluted vortex generator, U.S. Pat. No. 4,971,768; Serrated fan blade, U.S. Pat. No. 6,733,240; Wind turbine, U.S. Pat. No. 5,533,865; Spiral-based axial flow devices, U.S. Pat. No. 6,336,771; Multi-stage mixer/ejector for suppressing infrared radiation, U.S. Pat. No. 6,016,651; Serrated-planform lifting-surfaces U.S. Pat. No. 5,901,925; Serrated leech flaps for sails, U.S. Pat. No. 6,684,802; Serrated trailing edges for improving lift and drag characteristics of lifting surfaces, U.S. Pat. No. 5,088,665; Helicopter rotor with blade trailing edge tabs responsive to control system loading, U.S. Pat. No. 4,461,611; Jet Exhaust Noise Reduction system and Method, U.S. Pat. No. 7,114,323 B2; Quiet Chevron/Tab Exhaust Eductor System, U.S. Patent Publication US2006/0059891 A1.
It is known in the field of fluid dynamics, in particular within aeronautics, to apply the concept of wake vortex mitigation to reduce the influence of trailing vortex wakes of a lifting or thrust-generating body or wing by the addition of winglet structures at the wingtips thus reducing the induced drag due to the kinetic energy of such concentrated wake vortex structures generated by the lifting or thrust-generating surface as a whole.
Various methods of wake vortex control and drag alleviation have been proposed and are referenced within and the entire teachings of which and their references sited therein are expressly incorporated by reference herein. These include control surface oscillations, wingtip devices, multi-wake interactions, thermal forcing and mass/momentum injection.
The prior art includes several devices and methods that attempt to overcome the problem of concentrated vortex wakes. Several types of improvements have been proposed in an attempt to reduce the kinetic energy of vortex wakes. These include: Vortex Dissipator, U.S. Pat. No. 3,845,918; Vortex Diffusion and Dissipation, U.S. Pat. No. 4,046,336; Vortex Diffuser, U.S. Pat. No. 4,190,219; Vortex Alleviating Wing Tip, U.S. Pat. No. 4,447,042; Wingtip Airfoils, U.S. Pat. No. 4,595,160.
However, the above approaches do not eliminate the concentrated wake vortex generated at the wingtip. The “spiroid” wing tip of U.S. Pat. No. 5,102,068, Apr. 7, 1992, produces a reduction in induced drag, much like that of a winglet. Although a closed lifting or thrust-generating system may eliminate the wing tips, it does not eliminate the concentrated trailing wake vortex structure.
In order to significantly reduce the concentration of the trailing wake vortex structure and the associated kinetic energy there must be a change in the wing structure that promotes mixing of the upper fluid stream and lower fluid stream such that the fluid mixing or vortex-mixing is not forced to occur at the wing tip region as within the current state of the art. One example is that described within Lifting or thrust-generating Body with Reduced-Strength Trailing Vortices, U.S. Pat. No. 5,492,289 which produces a reduction in drag but does not eliminate the concentrated trailing wake vortex structure wherein vortex-mixing is forced to occur at the wing tip or control surface tip and is not distributed along the length of the wing span or control surfaces thereof.
Riblets are well known within the art for reducing drag. See, e.g., Steamwise Variable Height Riblets For Reduced Skin Friction Drag Of Surfaces, U.S. Pat. No. 6,345,791.
Compliant surfaces are also well known within the art for reducing drag. See, e.g., Shape Changing Structure, U.S. Pat. No. 7,216,831 B2; Morphing Structure, U.S. Patent Publication US2006/101807.
The above-discussed active and passive methods, although they do reduce induced drag for improvement in performance, provide no substantial decrease in rolling moment coefficients that generate wake vortexes. Thus there is a lack in the art for a truly effective and reliable method of trailing wake vortex mitigation.